With the advancement of information processing technologies in recent years, a packet switching network has become used in not only simple data transmission, such as sending and receiving e-mail, but also real-time communications, such as audio and video communications, for example, IP telephony and IP broadcasting.
For such real-time communications, monitoring and managing communication quality is especially important. This is because, for example, in the case of IP telephone, voice, which is carried in packets, may not be correctly carried if a packet delay or a packet loss occurs.
Traditionally used methods of monitoring communication quality may be classified into active and passive ones.
The active communication quality monitoring method is the one of actually measuring network performance by, for example, transmitting a test packet to a packet switching network and measuring its response time. For this method, it is necessary to send out many test packets to the packet switching network. With this method, it is impossible to identify the position of an abnormal event that occurred only once by transmitting a test packet after the occurrence of the abnormal event.
The passive communication quality monitoring method is the one of analyzing network quality by capturing a packet being transmitted in a packet switching network using a measurement device. With this method, although the position of a trouble may be roughly identified in accordance with the position of the measurement device, it is very difficult to precisely identify it.
A technique is proposed that collects, by a management manager, information regarding quality from monitoring agents arranged at a plurality of positions on a network and determining a zone at which the quality is degraded from the collected information (see Japanese Laid-open Patent Publication No. 2007-68093). With this technique, a zone at which the quality is degraded may be found.